1. Field of the Invention
The present invention relates to a method for direct link in a wireless communication system, and more particularly, to a method for achieving a direct link applied in a central managed wireless communication system with broadcast function.
2. Related Art
Along with the continual progress of communication technology, the manner in which people access networks is gradually evolving from narrow band to broad band, and the manner for internet connection is evolving from wired connections to wireless connections. The IEEE 802.16 wireless transmission manner especially receives the attention of the masses, it can be used to transmit high-speed data, and can further resist multi-path effect, eliminate interference among symbols, resist selective frequency fading, and has a high channel availability, such that network disposition is more convenient and flexible, especially effective in solving the most troublesome last mile problem of network construction.
Referring to FIG. 1, it is a schematic diagram of a conventional transmission manner in the IEEE 802.16 wireless network system. Taking two subscriber stations (SSs) as an example, connection request signalings 140 are first put forward to a base station (BS) 110 by SSs 120, 130; then the BS 110 determines whether or not to accept the connections of the first SS 120 and the second SS 130, according to the present state of the wireless environment.
Once the BS 110 accepts the connections of the first SS 120 and the second SS 130, the decision is added into a broadcast message 160 to inform the two SSs 120, 130, and unique connection IDs (CIDs) are assigned to the first SS 120 and the second SS130 respectively as a reference to distinguish the two different SSs 120, 130. In the IEEE 802.16 system, the BS 110 control all the wireless resource distributions, for distributing the wireless resource to each SS 120, 130 in a manner of time division duplex (TDD), and the BS 110 also may periodically send a broadcast message to the SSs 120, 130, for informing the SSs 120, 130, regarding data transmission 150, of when data can be uploaded and when data must be received.
As shown in FIG. 2a, it is a schematic diagram of a scheduling architecture of a frame 20. According to the IEEE 802.16 system, one or more UpLink burst (UL Burst) time slots in the UpLink SubFrame (UL SubFrame) 210 are required by the SSs 120, 130 to upload data, and one or more DownLink Burst (DL Burst) time slots in the DownLink SubFrame (DL SubFrame) 220 are required by the SSs 120, 130 to receive data. Such a data distribution manner will cause the following situations when a same data is switched between the two SSs 120, 130, as shown in FIG. 2b and 2c: in FIG. 2b, an SS A, and an SS C upload the “A→B data” and “C→D, E data” to the BS 110 in the nth frame respectively, while in FIG. 2c, an SS B, an SS D, and an SS E receive the “A→B data” and “C→D, E data” from the BS 110 in the (n+1)th frame respectively. And in such a manner, one or even multiple UL Burst time slots and one or more DL Burst time slots will be tied up more than normally, and data will appear in repeat in the UL SubFrame 210 and the DL SubFrame 220, thus wasting wireless resources. And the BS 110 should receive and transmit data between the two SSs 120, 130, and its loading is relatively heavy when the transmission is frequent.